1. Field of the Invention
This invention generally relates to a semiconductor device, and, in particular, to a clock regulation scheme for varying loads in a memory device, such as a flash memory.
2. Description of the Related Art
Advancements in the memory technology have resulted in improved memories at a lower price. For example, flash memories today store a greater number of bits per unit of area at an overall lower cost-per-megabyte. The affordable price of flash memory has made it a popular choice among many application developers.
Flash memory (sometimes called “flash RAM”) is a type of non-volatile memory that can be erased and reprogrammed in units of memory called blocks. Flash memory is a variation of electrically erasable programmable read-only memory (EEPROM) that, unlike flash memory, is erased and rewritten at the byte level, which is slower than block updating. Flash memory is commonly used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written in block (rather than byte) sizes, making it faster to update. Applications employing flash memory include digital cellular phones, digital cameras, LAN switches, computers, digital set-up boxes, embedded controllers, and other devices.
Flash memories sometimes employ a high voltage pump to generate a variety of different voltages. The pump output voltage desired is typically dictated by the mode of operation of the flash memory, where each mode of operation may have a different load and current requirement. The voltage pumps are commonly designed to handle the maximum load. Designing the voltage pumps to handle the maximum load, however, can create overshoot and ripple problems when the load is less than the maximum. With lighter loads, for example, the pump may overshoot its target regulation value because the delta output voltage with each input clock of the pump may be too great.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.